3 dirty intake runners?

juld0zer

Warped upper manifold Digi?? Is that what was causing your power loss issues?

Damn man, i hope you have finally sorted it out.

When i fitted my Motordyne manifold for testing, i dont recall noticing any variation in the soiling of the lower manifold. VQ37 has no EGR valve. All the EGR functions are performed via VVT (valve overlap). It shouldn't be exhaust soot because that would indicate a backfire through the intake.

I've never dissected an upper manifold before but i did stick a flashlight into it and have a look around. From what i remember, there are two inlets for the crankcase ventilation for a reason (i suspect there is a partition inside the manifold which separates the crankcase fumes from each bank) & that might have something to do with why one bank is soiled much more than the other. My car had approx 60,000km when i did the manifold swap and the lower manifold looked as 'clean' as your 'cleaner' bank. Like you, i was also very (pleasantly) surprised.

In summary, i'd check both your PCV lines and clean out the upper manifold with a generous amount of brake cleaner or a commercial parts washing machine then dry thoroughly.